1. Field of the Invention
The present invention relates to fire resistant sandwich boards intended for use as wall panels or ceilings in interiors of rooms subject to stringent fire codes, e.g. interiors on board ships, oil platforms or inside certain types of building structures. The invention further relates to methods of manufacturing such sandwich boards or intermediate products for this use.
2. The Prior Art
Various requirements applying to wall panels and ceilings for such applications e.g. related to cost, weight, heat insulation, sound insulation, resistance to wear, resistance to chemicals, aesthetic value in addition to fire hazard considerations have led to the introduction of sandwich boards in various forms. A sandwich board of relevance in the present context comprises a core of mineral wool with steel plate liners on both sides. For structural considerations the mineral wool core is preferably arranged with the fibres extending crosswise, i.e. so as to span the liner interspace and the liners adhered to the core by adhesive. Some examples of this kind of sandwich board are explained in Swedish patent publication No. SE 385 673. For reasons of aesthetic value it is commonly used to laminate the steel liners with plastic or to cover them with PVC foil. A PVC foil of a thickness 0.150 mm can be coloured and textured to provide an attractive appearance. Although a product of this kind satisfies most of the codes presently applied, the plastic laminate inevitably is a source of heat release and a source of harmful and poisonous gases when exposed to open fire. It has been suggested to cover the steel liners with a very thin layer of polymer material, e.g. a layer with a surface thickness of 0.030 mm in order to minimise heat release and gas release under fire exposure. However, such products have failed to gain acceptance on the market because of the lack of aesthetic value offered. The publication WO 95/30 552 contains the suggestion of building a sandwich wall panel with a metal liner with a decorative colouring, e.g. a reproduction of a photograph or of a piece of art. According to this publication the board panel is manufactured by stacking together various components among which metal foil and a transfer paper and by heat pressing the stack for a time period of 5 to 30 minutes whereby the dye transfers to the plate surface. EP-A 00 72 461 contains a suggestion for continuous printing of a steel plate of a thickness of 0.75 mm by a transfer process which takes place between a double band press. DE-C 26 42 350 and DE-C 29 14 704 offer various suggestions for dyes and printing methods related to transfer printing of textiles.
The solutions suggested in the prior art do not seem to have gained any share of the market in fireproof panels, presumably because the manufacturing methods are too cumbersome or costly or perhaps because they failed to come up with products which can truly meet all the applicable requirements.
The invention, in a first aspect, provides a method of manufacturing a coil of liner for use in the manufacturing of a sandwich board, said method comprising the steps of:
providing a continuous web of steel plate coated on one side with a layer of polyester with embedded polyamide spheres,
providing a continuous web of transfer material, which transfer material exhibits at least one face printed with indicia in a sublimable dye,
bringing said webs together with said printed face in surface contact with a face of said steel plate web,
running said contacting webs around part of the circumference of a heated roller while running a blanket around at least part of said roller in overlying relationship with said webs, said blanket being tensioned around said part of said roller in order to substantially prevent any slippage between said webs,
the extent of circumference covered by said webs, the speed of revolution of said roller, and the temperature of said roller being selected to allow a sublimation process to take place between said webs, which process yields a web of printed steel plate and a web of spent transfer material,
separating said web of spent transfer material from said web of printed steel plate,
air cooling said web of printed steel plate until the print has cured,
bringing a web of polymer foil together with said web of printed steel plate in bonded contact whereby to provide a liner, and
cutting a length of said liner and winding it on a liner take-up roll, whereby to provide said coil.
This provides a highly efficient manufacturing method adapted for outputting a liner by means of which it is possible to manufacture a sandwich board, which board satisfies all the requirements mentioned above and which exhibits a performance during fire tests superior to those achieved by the majority of boards on the market today. The liner is imprinted by way of a transfer process which permits a large variety of colours and patterns. The surface finish is highly resistant to wear and the product may be shipped with a protective covering which may stay in place preserving the surface finish until one of the last stages of room finishing.
The invention, in a second aspect, provides a method of manufacturing a fire resistant sandwich board comprising the steps of:
providing a continuous web of steel plate coated on one side with a layer of polyester with embedded polyamide spheres,
providing a continuous web of transfer material, which transfer material exhibits at least one face printed with indicia in a sublimable dye,
bringing said webs together with said printed face in surface contact with a face of said steel plate web,
running said contacting webs around part of the circumference of a heated roller while running a blanket around at least part of said roller in overlying relationship with said webs, said blanket being tensioned around said part of said roller in order to substantially prevent any slippage between said webs,
the extent of circumference covered by said webs, the speed of revolution of said roller, and the temperature of said roller being selected to allow a sublimation process to take place between said webs, which process yields a web of printed steel plate and a web of spent transfer material,
separating said web of spent transfer material from said web of printed steel plate,
air cooling said web of printed steel plate until the print has cured,
bringing a web of polymer foil together with said web of printed steel plate in bonded contact whereby to provide a liner,
cutting a length of said liner and winding it on a liner take-up roll, whereby to provide a coil,
forming a web of liner by unwinding said coil,
cutting from said liner web a pair of substantially identical sections,
placing said sections and said board in overlying sandwich arrangement and adhering said sections with said board, and
subjecting the sandwich to pressure and heat in order to cure the adhesive.
This provides the manufacturing of a sandwich board capable of meeting the strictest fire requirements and capable of meeting also the multitude of other requirements referred to above. The board can be manufactured at comparatively low cost.
The invention, in a third aspect, provides a fire resistant sandwich board comprising a mineral wool board core and a pair of steel plate liners adhered onto respective sides of said core, at least one of said steel plate liners being surface treated on a side facing away from the core with a coating, which coating comprises polyester with embedded polyamide spheres and a top finish with a decorative pattern, which top finish has been applied by way of sublimation process.
This board meets all requirements relevant to a board for use as interior wall panel or ceiling as explained above.
Preferred embodiments appear from the dependent claims.